Trust relationship migration for data mirroring

ABSTRACT

One or more techniques and/or systems are provided for migrating a trust relationship. For example, a first storage cluster and a second storage cluster have a disaster recovery relationship where the second storage cluster provides failover client access to replicated data, replicated from the first storage cluster to the second storage cluster, in the event the first storage cluster fails. The first storage cluster may have a trust relationship with a third storage cluster, such that data is mirrored from a volume of the first storage cluster into a mirrored volume of the third storage cluster based upon the trust relationship. In the event the first storage cluster fails over to the second storage cluster due to a disaster at the first storage cluster, the trust relationship is migrated to be between the second storage cluster and the third storage cluster for non-disruptive mirroring of data to the mirrored volume.

RELATED APPLICATION

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 15/820,940, filed on Nov. 22, 2017 and titled“TRUST RELATIONSHIP MIGRATION FOR DATA MIRRORING,” which claims priorityto and is a continuation of U.S. Pat. No. 9,836,367, filed on Aug. 28,2015 and titled “TRUST RELATIONSHIP MIGRATION FOR DATA MIRRORING,” whichare incorporated herein by reference.

BACKGROUND

A storage network environment may comprise one or more storage clustersof storage controllers (e.g., nodes) configured to provide clients withaccess to user data stored within storage devices. For example, a firststorage cluster may comprise a first storage controller configured toprovide clients with access to user data stored within a first storagedevice. A second storage cluster may be configured according to adisaster recovery relationship with respect to the first storagecluster, such that user data (e.g., user files, applications, etc.) andconfiguration data (e.g., volume information, a replication policy, anetwork interface configuration, etc.) are replicated from the firststorage cluster to the second storage cluster. In this way, when adisaster occurs at the first storage cluster and clients are unable toaccess user data within the first storage device because the firststorage controller may be unavailable or may have failed from thedisaster, a second storage controller of the second storage cluster mayprovide clients with failover client access to replicated user data thatwas replicated from the first storage device to a second storage deviceaccessible to the second storage controller. When the first storagecluster recovers from the disaster, the second storage cluster mayswitch back to the first storage cluster such that the first storagecontroller provides clients with access to user data from the firststorage device (e.g., the first storage device may be synchronized withany changes made to user data and/or configuration data within thesecond storage device during switchover operation by the second storagecontroller). In this way, user data and configuration data may be backedup between storage clusters for disaster recovery.

Because a client may be unable to access the replicated user data on thesecond storage cluster due to the disaster recovery relationship (e.g.,client access to the second storage device may be restricted because thesecond storage device is a backup storage device for disaster recovery),the client may request a trust relationship between the first storagecluster and a third storage cluster where the trust relationshipspecifies that data from the first storage cluster can be mirrored tothe third storage cluster for client backup and/or access by the client.In an example, the trust relationship may be established based uponstorage administrators of the first storage cluster and the thirdstorage cluster coming to an agreement regarding the mirroring of data(e.g., an agreement that a volume of a virtual storage machine of thefirst storage cluster can mirror data to a mirrored volume of a secondvirtual storage machine of the third storage cluster). Unfortunately, ifthe first storage cluster experiences a disaster and the second storagecluster takes over for the first storage cluster using a switchoveroperation, the trust relationship is broken and an interruption inmirroring of data to the third storage cluster will occur until a newtrust relationship is manually established by the client between storageadministrators of the second storage cluster and the third storagecluster (e.g., if the client is unaware of the broken trustrelationship, then the client may inadvertently forgo setting up the newtrust relationship, thus losing any mirroring of data to the thirdstorage cluster).

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of migrating atrust relationship.

FIG. 4A is a component block diagram illustrating an exemplary systemfor migrating a trust relationship, where a disaster recoveryrelationship is established between a first storage cluster and a secondstorage cluster.

FIG. 4B is a component block diagram illustrating an exemplary systemfor migrating a trust relationship, where a trust relationship, formirroring data, is established between a first storage cluster and athird storage cluster.

FIG. 4C is a component block diagram illustrating an exemplary systemfor migrating a trust relationship, where a trust relationship ismigrated to create a migrated trust relationship based upon a switchoveroperation.

FIG. 4D is a component block diagram illustrating an exemplary systemfor migrating a trust relationship, where a migrated trust relationshipis migrated to create a restored trust relationship based upon aswitchback operation.

FIG. 5 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more systems and/or techniques for migrating a trust relationshipare provided. A first storage cluster and a second storage cluster maybe configured according to a data protection relationship (e.g.,replication of data from a storage cluster to another storage clusterfor data replication and redundancy) and/or a disaster recoveryrelationship (e.g., when a storage cluster fails, a switchover toanother storage cluster is performed for failover client access toreplicated data), such that the user data and configuration data of thefirst storage cluster may be replicated from the first storage clusterto the second storage cluster so that the second storage cluster mayprovide failover client access to replicated user data in the event adisaster occurs at the first storage cluster. Similarly, user data andconfiguration data of the second storage cluster may be replicated fromthe second storage cluster to the first storage cluster so that thefirst storage cluster may provide failover access to replicated userdata in the event a disaster occurs at the second storage cluster.

Because a client may be unable to access replicated user data, theclient may establish a mirroring relationship between the first storagecluster and a third storage cluster for mirroring data, such asmirroring data from a volume of the first storage cluster to a mirroredvolume within the third storage cluster. Unfortunately, if the firststorage cluster fails and a switchover operation to the second storagecluster is performed, then the trust relationship is broken and datamirroring to the third storage cluster is lost until a new trustrelationship is manually created. Accordingly, as provided herein, thetrust relationship may be automatically migrated (e.g., automatictriggering based upon a disaster of the first storage cluster and/orbased upon the switchover operation) so that data (e.g., replicateddata) is mirrored from the second storage cluster to the third storagecluster. In this way, non-disruptive data mirroring, such as volumelevel data mirroring, of data to the third storage cluster may bemaintained based upon the trust relationship and the migrated trustrelationship.

To provide context for trust relationship migration, FIG. 1 illustratesan embodiment of a clustered network environment 100 or a networkstorage environment. It may be appreciated, however, that thetechniques, etc. described herein may be implemented within theclustered network environment 100, a non-cluster network environment,and/or a variety of other computing environments, such as a desktopcomputing environment. That is, the instant disclosure, including thescope of the appended claims, is not meant to be limited to the examplesprovided herein. It will be appreciated that where the same or similarcomponents, elements, features, items, modules, etc. are illustrated inlater figures but were previously discussed with regard to priorfigures, that a similar (e.g., redundant) discussion of the same may beomitted when describing the subsequent figures (e.g., for purposes ofsimplicity and ease of understanding).

FIG. 1 is a block diagram illustrating an example clustered networkenvironment 100 that may implement at least some embodiments of thetechniques and/or systems described herein. The example environment 100comprises data storage systems or storage sites 102 and 104 that arecoupled over a cluster fabric 106, such as a computing network embodiedas a private Infiniband, Fibre Channel (FC), or Ethernet networkfacilitating communication between the storage systems 102 and 104 (andone or more modules, component, etc. therein, such as, nodes 116 and118, for example). It will be appreciated that while two data storagesystems 102 and 104 and two nodes 116 and 118 are illustrated in FIG. 1,that any suitable number of such components is contemplated. In anexample, nodes 116, 118 comprise storage controllers (e.g., node 116 maycomprise a primary or local storage controller and node 118 may comprisea secondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets. Illustratively, the host devices 108, 110 may begeneral-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more networkconnections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in a datastorage and management network cluster environment 100 can be a deviceattached to the network as a connection point, redistribution point orcommunication endpoint, for example. A node may be capable of sending,receiving, and/or forwarding information over a network communicationschannel, and could comprise any device that meets any or all of thesecriteria. One example of a node may be a data storage and managementserver attached to a network, where the server can comprise a generalpurpose computer or a computing device particularly configured tooperate as a server in a data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the exemplary environment 100, nodes 116, 118 cancomprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise a network module 120, 122 and a data module 124, 126.Network modules 120, 122 can be configured to allow the nodes 116, 118(e.g., network storage controllers) to connect with host devices 108,110 over the network connections 112, 114, for example, allowing thehost devices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1, a first network module 120 of first node 116 canaccess a second data storage device 130 by sending a request through asecond data module 126 of a second node 118.

Data modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, data modules 124, 126 communicate with the data storage devices128, 130 according to a storage area network (SAN) protocol, such asSmall Computer System Interface (SCSI) or Fiber Channel Protocol (FCP),for example. Thus, as seen from an operating system on a node 116, 118,the data storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the example embodiment 100illustrates an equal number of network and data modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and data modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and data modules. That is, differentnodes can have a different number of network and data modules, and thesame node can have a different number of network modules than datamodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the networking connections 112, 114. As an example,respective host devices 108, 110 that are networked to a cluster mayrequest services (e.g., exchanging of information in the form of datapackets) of a node 116, 118 in the cluster, and the node 116, 118 canreturn results of the requested services to the host devices 108, 110.In one embodiment, the host devices 108, 110 can exchange informationwith the network modules 120, 122 residing in the nodes (e.g., networkhosts) 116, 118 in the data storage systems 102, 104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. Volumes can span a portion of a disk, acollection of disks, or portions of disks, for example, and typicallydefine an overall logical arrangement of file storage on disk space inthe storage system. In one embodiment a volume can comprise stored dataas one or more files that reside in a hierarchical directory structurewithin the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the example environment 100, the host devices 108, 110 can utilizethe data storage systems 102, 104 to store and retrieve data from thevolumes 132. In this embodiment, for example, the host device 108 cansend data packets to the network module 120 in the node 116 within datastorage system 102. The node 116 can forward the data to the datastorage device 128 using the data module 124, where the data storagedevice 128 comprises volume 132A. In this way, in this example, the hostdevice can access the storage volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the host 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The host 118 can forward the data to the data storagedevice 130 using the data module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that trust relationship migration may beimplemented within the clustered network environment 100. For example, arelationship migration component may be implemented for the node 116and/or the node 118. The relationship migration component may beconfigured to migrate a trust relationship between the node 116 and thenode 118 (e.g., data may be mirrored from the node 116 to the node 118based upon the trust relationship) to another node. For example,responsive to the node 116 having a disaster and switching over to asecond node with which the node 116 has a disaster recoveryrelationship, the trust relationship may be migrated as a migrated trustrelationship between the second node and the node 118 for datamirroring.

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The example data storage system 200 comprisesa node 202 (e.g., host nodes 116, 118 in FIG. 1), and a data storagedevice 234 (e.g., data storage devices 128, 130 in FIG. 1). The node 202may be a general purpose computer, for example, or some other computingdevice particularly configured to operate as a storage server. A hostdevice 205 (e.g., 108, 110 in FIG. 1) can be connected to the node 202over a network 216, for example, to provides access to files and/orother data stored on the data storage device 234. In an example, thenode 202 comprises a storage controller that provides client devices,such as the host device 205, with access to data stored within datastorage device 234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software application code and datastructures. The processors 204 and adapters 210, 212, 214 may, forexample, include processing elements and/or logic circuitry configuredto execute the software code and manipulate the data structures. Theoperating system 208, portions of which are typically resident in thememory 206 and executed by the processing elements, functionallyorganizes the storage system by, among other things, invoking storageoperations in support of a file service implemented by the storagesystem. It will be apparent to those skilled in the art that otherprocessing and memory mechanisms, including various computer readablemedia, may be used for storing and/or executing application instructionspertaining to the techniques described herein. For example, theoperating system can also utilize one or more control files (not shown)to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a computer network 216, which may comprise, amongother things, a point-to-point connection or a shared medium, such as alocal area network. The host device 205 (e.g., 108, 110 of FIG. 1) maybe a general-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network connection 216 (and/or returned toanother node attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on arrays 218, 220, 222 can beimplemented as one or more storage “volumes” 230, 232 that are comprisedof a cluster of disks 224, 226, 228 defining an overall logicalarrangement of disk space. The disks 224, 226, 228 that comprise one ormore volumes are typically organized as one or more groups of RAIDs. Asan example, volume 230 comprises an aggregate of disk arrays 218 and220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the LUNs 238.

It may be appreciated that trust relationship migration may beimplemented for the data storage system 200. For example, a trustrelationship component may be implemented for the node 202. Therelationship migration component may be configured to migrate a trustrelationship between the node 202 and a second node (e.g., data may bemirrored from the node 202 to the second node based upon the trustrelationship) to another node. For example, responsive to the node 202having a disaster and switching over to a third node with which the node202 has a disaster recovery relationship, the trust relationship may bemigrated as a migrated trust relationship between the third node and thesecond node for data mirroring.

One embodiment of migrating a trust relationship is illustrated by anexemplary method 300 of FIG. 3. At 302, a first storage cluster and asecond storage cluster may be determined as having a disaster recoveryrelationship where user data and configuration data (e.g., volumeinformation, LUN information, snapshot policy information, networkinterface information, routing route information, IP information, etc.)is synchronously or asynchronously replicated from the first storagecluster to the second storage cluster. For example, a first storagecontroller of the first storage cluster may provide primary clientaccess to user data stored within a first storage object (e.g., a firststorage virtual machine comprising a volume) comprised within the firststorage cluster. The user data and configuration data of the firststorage object may be replicated to the second storage cluster, such asinto a second storage object having a disaster recovery backuprelationship with the first storage object (e.g., into a replicatedvolume, of a second storage virtual machine comprised within the secondstorage object, that is a disaster recovery backup of the volume), sothat a second storage controller may provide failover client access toreplicated user data within the second storage object in the event adisaster occurs at the first storage cluster.

Responsive to the first storage cluster recovering from the disaster,the second storage cluster may switch back control to the first storagecluster for providing primary client access to user data from the firststorage object (e.g., the first storage object may be synchronized withany changes made to user data and/or configuration data within thesecond storage object). Because the second storage object has thedisaster recovery backup relationship with the first storage object, aclient may be unable to access the second storage object (e.g., theclient may be restricted from accessing the replicated volume within thesecond storage cluster).

At 304, a trust relationship, for mirroring data from the first storagecluster to a third storage cluster, may be determined to exist betweenthe first storage object of the first storage cluster (e.g., the firststorage virtual machine such as the volume) and a third storage objectof the third storage cluster (e.g., a third storage virtual machinecomprising a mirrored volume that is a mirror of the volume). Forexample, the trust relationship may specify that data of the volume ofthe first storage virtual machine within the first storage cluster is tobe mirrored into the mirrored volume of the third storage virtualmachine within the third storage cluster. In an example, the firststorage cluster and the third storage cluster have a non-disasterrecovery relationship, such that a client may be provided with access tothe third storage object, such as the mirrored volume (e.g., readaccess, modify access, mount access, or any other volume operationaccess to the mirrored volume). In this way, the trust relationship mayspecify that the first storage cluster is the data mirroring source forthe third storage cluster.

At 306, responsive to determining that the second storage cluster isproviding failover client access, based upon the disaster recoveryrelationship, to data (e.g., replicated data within the replicatedvolume) in place of the first storage cluster due to the first storagecluster having a disaster, the trust relationship may be migrated frombetween the first storage cluster and the third storage cluster to beingbetween the second storage cluster and the third storage cluster tocreate a migrated trust relationship for mirroring data from the secondstorage cluster to the third storage cluster (e.g., migrating data fromthe replicated volume of the second storage cluster to the mirroredvolume of the third storage cluster). The migrated trust relationshipmay specify that data of the second storage object within the secondstorage cluster (e.g., data within the replicated volume because thereplicated volume is a disaster recovery backup of the volume within thefirst storage cluster) is to be mirrored to the third storage object,such as the mirrored volume, of the third storage cluster. In this way,the migrated trust relationship may specify that the second storagecluster is the data mirroring source for the third storage cluster. Inan example, the migration may be automatically triggered based upon atrigger event such as based upon detection of the first storage clusterexperiencing the disaster and/or based upon detection that the secondstorage cluster is providing failover client access to data in place ofthe first storage cluster.

In an example, the first storage cluster may recover from the disaster,and the second storage cluster may switch back to the first storagecluster such that the first storage cluster is providing primary clientaccess to data, such as data within the volume of the first storagevirtual machine (e.g., the volume may be synchronized with any changesto user data and/or configuration data within the replicated volumeduring switchover operation). Responsive to identifying the switchback,the migrated trust relationship may be migrated back from between thesecond storage cluster and the third storage cluster to being betweenthe first storage cluster and the third storage cluster to create arestored trust relationship for mirroring data from the first storagecluster to the third storage cluster. In this way, non-disruptive volumelevel data mirroring of data to the third storage cluster, such as themirrored volume, may be maintained based up the trust relationship, themigrated trust relationship, and/or the restored trust relationship.

FIGS. 4A-4D illustrate examples of a system 400, comprising arelationship migration component 401, for migrating a trustrelationship. FIG. 4A illustrates a storage cluster (A) 402 and astorage cluster (B) 408 having data protection relationship 414 (e.g.,indicating that data is to be replicated from the storage cluster (A)402 to the storage cluster (B) 408 for backup data protection) and/or adisaster recovery relationship 416 (e.g., indicating that the storagecluster (B) 408 is to provide failover client access to data in place ofthe storage cluster (A) 402 in the event the storage cluster (A) 402experiences a disaster), where changes to user data and configurationdata managed by the storage cluster (A) 402 are backed up to the secondstorage cluster (B) 408, and changes to user data and configuration datamanaged by the storage cluster (B) 408 are backed up to the storagecluster (A) 402. For example, the storage cluster (A) 402 may comprise astorage virtual machine 404 comprising a volume 406. The storage cluster(A) 402 may provide a client 401 with access 418 to the volume 406(e.g., the client 401 may store, retrieve, and/or modify database files,application data, and/or other user files within the volume 406).

Because of the data protection relationship 414 and/or the disasterrecovery relationship 416, a backup disaster recovery storage virtualmachine 410 may be maintained by the storage cluster (B) 408 as a backupfor the volume 406 in the event a disaster occurs at the storage cluster(A) 402. The backup disaster recovery storage virtual machine 410 maycomprise a backup disaster recovery volume 412 into which data of thevolume 406 is replicated to create replicated backup data. In this way,user data and/or configuration data of the volume 406 is replicated intothe backup disaster recovery volume 412 so that the storage cluster (B)408 may provide the client 401 with failover access to replicated backupdata within the backup disaster recovery volume 412 in the event thestorage cluster (A) 402 fails and the client 401 is unable to access thevolume 406.

FIG. 4B illustrates an example of the relationship migration component403 identifying a trust relationship 427. For example, the client 401may request for the trust relationship 427 to be established between thestorage virtual machine 404 and a second storage virtual machine 422hosted on a storage cluster (C) 420 (e.g., a storage cluster with whichthe storage cluster (A) 402 does not have a disaster recoveryrelationship). In an example, the trust relationship 427 may be agreedupon by storage administrators of the storage cluster (A) 402 and thestorage cluster (C) 420 so that data of the volume 406 can be mirrored426 into a mirrored volume 424 within the second storage virtual machine422. In this way, the client 401 may access the mirrored volume 424 forreading, modifying, mounting, and/or performing other volume leveloperations because the client 401 may otherwise not have such access tothe backup disaster recovery volume 412 within the storage cluster (B)408 due to the disaster recovery relationship 416.

FIG. 4C illustrates an example of the relationship migration component403 triggering migration of the trust relationship 427 based upon aswitchover 453 from the storage cluster (A) 402 to the storage cluster(B) 408. For example, a disaster 452 may occur at the storage cluster(A) 402, such that the client 401 is unable to access the volume 406through the storage cluster (A) 402. In response to the disaster 452,the switchover 453 may be performed where the storage cluster (B) 408provides the client 401 with access 454 to replicated data, replicatedfrom the volume 406 to the backup disaster recovery volume 412, withinthe backup disaster recovery volume 412 in place of the storage cluster(A) 402 based upon the disaster recovery relationship 416.

Accordingly, the relationship migration component 403 may migrate thetrust relationship 427 from being between the storage cluster (A) 402and the storage cluster (C) 420 to being between the storage cluster (B)408 and the storage cluster (C) 420 to create a migrated trustrelationship 456. The migrated trust relationship 456 may specify thatthe storage cluster (B) 408 is a mirroring source for mirroring datafrom the backup disaster recovery volume 412 to the mirrored volume 424(e.g., the migrated trust relationship 456 replaces the trustrelationship 427, lost due to the disaster 452, that specified that thestorage cluster (A) 402 was the mirroring source for mirroring data fromthe volume 406 to the mirrored volume 424). Because the backup disasterrecovery volume 412 comprises replicated data of the volume 406 and isnow servicing the client 401 for accessing 454 the replicated data ofthe backup disaster recovery volume 412, up-to-date data may be mirroredfrom the backup disaster recovery volume 412 into the mirrored volume424 based upon the migrated trust relationship 456. In this way,non-disruptive volume level data mirroring of data to the storagecluster (C) 420, such as into the mirrored volume 424, may be maintainedbased upon the relationship migration component 403 automaticallymigrating the trust relationship 427 to create the migrated trustrelationship 456, which may mitigate data loss otherwise occurring ifthe trust relationship 456 was not automatically created from themigration because mirroring of data would otherwise have stopped until anew trust relationship was manually recreated.

FIG. 4D illustrates an example of a switchback operation 460 beingperformed based upon restoration of the storage cluster (A) 402 into anoperational state. For example, the storage cluster (A) 402 may recoverfrom the disaster 452 such that the storage virtual machine 404 and thevolume 406 may be made accessible 470 to the client 401 based upon theswitchback operation 460 (e.g., the volume 406 may be synchronized withthe backup disaster recovery volume 412 so that the volume 406 reflectsdata changes made to the backup disaster recovery volume 412 while thestorage cluster (A) 402 was inoperable).

Accordingly, the relationship migration component 403 may migrate themigrated trust relationship 456 from between the storage cluster (B) 408and the storage cluster (C) 420 to being between the storage cluster (A)402 and the storage cluster (C) 420 to create a restored trustrelationship 462. The restored trust relationship 462 may specify thatthe storage cluster (A) 402 is the mirroring source for mirroring datafrom the volume 406 to the mirrored volume 424. In this way,non-disruptive volume level data mirroring of data to the storagecluster (C) 420, such as into the mirrored volume 424, may be maintainedbased upon the relationship migration component 403 automaticallymigrating the migrated trust relationship 456 to create the restoredtrust relationship 462, which may mitigate data loss otherwise occurringif the restored trust relationship 462 was not automatically createdfrom the migration because mirroring of new data changes to the volume406 would not otherwise be mirrored to the mirrored volume 424 until anew trust relationship was manually recreated.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 5, wherein the implementation 500comprises a computer-readable medium 508, such as a CD-ft DVD-R, flashdrive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 506. This computer-readable data 506, such asbinary data comprising at least one of a zero or a one, in turncomprises a set of computer instructions 504 configured to operateaccording to one or more of the principles set forth herein. In someembodiments, the processor-executable computer instructions 504 areconfigured to perform a method 502, such as at least some of theexemplary method 300 of FIG. 3, for example. In some embodiments, theprocessor-executable instructions 504 are configured to implement asystem, such as at least some of the exemplary system 400 of FIGS.4A-4D, for example. Many such computer-readable media are contemplatedto operate in accordance with the techniques presented herein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), EEPROM and/or flash memory, CD-ROMs, CD-Rs, CD-RWs, DVDs,cassettes, magnetic tape, magnetic disk storage, optical or non-opticaldata storage devices and/or any other medium which can be used to storedata.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: hosting a first virtualmachine at a first node, wherein a client device is provided with readand write access to first storage provided by the first virtual machine;hosting a second virtual machine at a second node; in response toreceiving a request from the client device to establish a trustrelationship between the first virtual machine and the second virtualmachine, establishing the trust relationship to specify the first nodeas data mirroring source for the second node; establishing anon-disaster recovery relationship between the first node and the secondnode; mirroring user data and configuration data from the first storageof the first virtual machine to second storage provided by the secondvirtual machine based upon the trust relationship being established; andproviding the client device with read and write access to the secondstorage.
 2. The method of claim 1, wherein the first storage provided bythe first virtual machine comprises cloud storage of a data cloud. 3.The method of claim 1, wherein the second storage provided by the secondvirtual machine comprises cloud storage of a data cloud.
 4. The methodof claim 1, comprising: detecting that the trust relationship is brokenbased upon the first node failing, wherein the mirroring of the userdata and the configuration data is stopped based upon the trustrelationship breaking.
 5. The method of claim 4, comprising: in responseto determining that the first node has recovered from the failure,automatically creating a restored trust relationship between the firstvirtual machine as the second virtual machine.
 6. The method of claim 5,comprising: resuming the mirroring of the user data and theconfiguration data based upon the restored trust relationship beingautomatically created.
 7. The method of claim 1, comprising: hosting atleast one of the first virtual machine or the second virtual machine ina data cloud.
 8. The method of claim 1, comprising: establishing thetrust relationship based upon an agreement by a storage administrator ofthe first node.
 9. The method of claim 1, comprising: establishing thetrust relationship based upon an agreement by a storage administrator ofthe second node.
 10. The method of claim 1, comprising: providing theclient device with volume mount access through second virtual machinebased upon the trust relationship.
 11. The method of claim 1,comprising: providing the client device with volume level operationsthrough second virtual machine based upon the trust relationship.
 12. Acomputing device, comprising: a processor; and a memory containinginstructions, which when executed by the processor, cause the processorto: host a first virtual machine at a first node, wherein a clientdevice is provided with read and write access to first cloud storageprovided by the first virtual machine; host a second virtual machine ata second node; in response to receiving a request from the client deviceto establish a trust relationship between the first virtual machine andthe second virtual machine, establish the trust relationship to specifythe first node as data mirroring source for the second node; establish anon-disaster recovery relationship between the first node and the secondnode; mirror data from the first cloud storage of the first virtualmachine to second cloud storage provided by the second virtual machinebased upon the trust relationship being established; and provide theclient device with read and write access to the second cloud storage.13. The computing device of claim 12, wherein the instructions cause theprocessor to: detect that the trust relationship is broken based uponthe first node failing, wherein the mirroring of the data is stoppedbased upon the trust relationship breaking.
 14. The computing device ofclaim 13, wherein the instructions cause the processor to: in responseto determining that the first node has recovered from the failure,automatically create a restored trust relationship between the firstvirtual machine as the second virtual machine.
 15. The computing deviceof claim 14, wherein the instructions cause the processor to: resume themirroring of the data based upon the restored trust relationship beingautomatically created.
 16. A non-transitory machine readable mediumcomprising instructions for performing a method, which when executed bya machine, causes the machine to: host a first virtual machine at afirst node, wherein a client device is provided with read and writeaccess to first cloud storage provided by the first virtual machine;host a second virtual machine at a second node; establish a trustrelationship to specify the first node as data mirroring source for thesecond node; establish a non-disaster recovery relationship between thefirst node and the second node; mirror data from the first cloud storageof the first virtual machine to second cloud storage provided by thesecond virtual machine based upon the trust relationship beingestablished; and provide the client device with read and write access tothe second cloud storage.
 17. The non-transitory machine readable mediumof claim 16, wherein the instructions cause the machine to: detect thatthe trust relationship is broken based upon the first node failing,wherein the mirroring of the data is stopped based upon the trustrelationship breaking.
 18. The non-transitory machine readable medium ofclaim 17, wherein the instructions cause the machine to: in response todetermining that the first node has recovered from the failure,automatically create a restored trust relationship between the firstvirtual machine as the second virtual machine.
 19. The non-transitorymachine readable medium of claim 18, wherein the instructions cause themachine to: resume the mirroring of the data based upon the restoredtrust relationship being automatically created.
 20. The non-transitorymachine readable medium of claim 16, wherein the instructions cause themachine to: provide the client device with volume level operationsthrough second virtual machine based upon the trust relationship.